Exhaust Heat Shield

Tamiya M41 Walker Bulldog Project — Exhaust Heat Shield Rust & Weathering Technique

IMG_1363Below are my steps used to achieve a realistic rusty appearance to the exhausts on the Tamiya M41 Walker Bulldog kit.


  1. Airbrush a base of red-brown per your liking, but aim to simulate a rusty tone.  I used a mix of Tamiya Flat Red (XF-7) and Flat Brown (XF-10).
  2. Spray/Airbrush on a chipping medium.  I used Ammo by Mig brand.

NOTE 1: “Ammo by Mig” are my preferred weathering products b/c application matches expectations


  1. Base coat OLIVE DRAB to match the muffler to the rest of the vehicle’s base color.
    1. I’m assuming but didn’t verify, this was how these units came from the factory.  Likely a bad assumption.
    2. My O.D. was a custom mix of the new Tamiya Lacquer Paint Olive Drab (LP-28), Olive Drab # 2 (LP-29) and a splash of Buff (LP-75) to lighten it.
    3. I lighten all my Tamiya mixes with buff instead of white to keep it on the warmer, dustier side.  I feel like I can always coat with a thin layer of buff for a dusty look as a much needed blend layer if contrast is suddenly too stark.


  1. Chip off the Olive Drab.
    1. Using a damp sponge and a cheap, stiff paint brush (I trim some of the bristles as required to stiffen)…I slowly chipped away the outer O.D. layer.
    2. I used the sponge more than the brush.
    3. My goal was to try to leave some of O.D. around the outer edges to look like overspray had built up on the muffler and started to bake off.


NOTE 2: Again, I didn’t reference and verify this…its just how I’ve seen mufflers and heat shields age from other real world examples.

NOTE 3: The rest of this involves pigments, and I make sure to put down a disposable drop cloth to catch the mess…more pigment ends up under the model than on it


  1. I applied AK Interactive, Dark Rust pigment Powder with my stiff brush, stippling back and forth with pigment and then a little bit of pigment fixer.
    1. I used Ammo by Mig fixer but IPA will work.
    2. The Fixer product was hotter than the IPA so keep that in mind with the base finish you are working with when selecting a fixer.
    3. I only use 91% IPA…not sure if this makes a difference, but its my only IPA data point
  1. I applied sparse amounts of AK Interactive Ochre Rust (aka Yellow) pigment in the same method for tone modulation.
  2. Proceeded to apply various combination of ground, soft pastels  using brown, orange, red and yellow to please my Mark 1 eyeball.  IPA as a fixer here works.  Let the pigment dry and cure.
  3. I then applied a back-and-forth combo of AK Interactive’s Exhaust Wash and Ammo’s Fixer with more pigments to build a rusty texture to the muffler.  I used a stippling action with my stiff brush to assist achieving my texture.
  4. Let dry, then inspect.  Repeat until you have a color, texture you are satisfied with.
Paints & Pigments used: